铝电解中的电极过程——Ⅰ. 阳极过程

研究了铝电解中的阳极反应、阳极过电压、电解质对炭电极的湿润性、双电层电容、交流阻抗、阳极效应等阳极过程,得出了可以相互证明的结论.①在阳极区可发生5个电化学反应,阳极产物分别是CO,CO2,COF2,CF4和F2;②在电流密度为0.02～1.2A/cm2范围内符合Tafel方程*反应控制步骤为化学反应CxO·O分解反应的迟滞,反应级数为0.5级;③测量了冰晶石-氧化铝熔体在石墨电极上的湿润性和双电层电容.发现在1.0V左右,湿润角有一最大值,双电层电容有一最小值,因此认为此电位为零电荷电位;④提出了发生阳极效应的新机理*认为当电解质中Al2O3质量分数＜2%时,是F-离子放电引起的阳极效应,而当Al2O3质量分数＞2%时,阳极效应的发生是因为阳极气体的阻塞

Electrode Processes in Aluminium Electrolysis:Ⅰ Anodic Process

The anodic processes in aluminium electrolysis,such as,anodicreaction,anodic overvoltage,the wettability of the carbon by the molten cryolite-alumina,the double layer capacitanic,the ac-faradic impedance and the anode effect,were studied. It is found that:① in the potential region of 0.5～4.5V there are five current peaks corresponding to the maximum rate of formation CO,CO2,COF2,CF4,and F2;② in the Tafel region (0.02～1.2A/cm2), the rate determing step of the anode over-voldepends on a reaction of dischaging of F- ion on carbon anode;③ a comparison of the wetting angle curve with the double layer capacitance shows that the maximum point on former curve is just opposite to the minimum point on the latter curve. This may be corresponding to the zero charge potential;④ a new mechannism of anode effect was suggested that when cAl2O3]＜2%,anode effect was caused by the discharging of F- on carbon anode,but when cAl2O3]＞2%,anode effect was caused by block CO2 bubbles.